1. Field
One or more example embodiments relate to a wireless communication apparatus, and more particularly, to a high frequency amplifying circuit for reducing occurrence of oscillation.
2. Description of Related Art
A high frequency amplifier circuit may include a transistor and a resonance load. However, due to a feature of a radio frequency (RF) corresponding to a high frequency, a stability may be reduced by a feedback effect caused by a parasite element of the transistor.
To solve a problem that the stability is reduced, several methods are proposed. A method of increasing a degree of isolation between an input end and an inductance-capacitance (LC) tank, a method of applying an additional negative feedback, and a method of compensating for a feedback factor are proposed.
However, the method of increasing the degree of isolation may require that a supply voltage should be as high as an operating condition of an additional transistor because the additional transistor is disposed on top of an original transistor such that an amount of power consumption increases. In addition, a gain may be reduced due to a signal leakage caused by a parasitic element increasing at a connection point between transistors.
The method of applying the additional negative feedback may have a disadvantage that a gain is reduced. As a result, a plurality of amplifying operations is required such that the amount of power consumption may increase. Also, an additional inductor is required except for a matching circuit of an input end. An increased area of the inductor may reduce an economic efficiency.
The method of compensating for the feedback factor may remove such effect from a resonance frequency by using a feedback capacitor CF and a feedback inductor LF corresponding to a main factor that causes oscillation by reducing the stability. However, an operation bandwidth is relatively narrow because the method of compensating for the feedback factor is only performed at a resonance point of the feedback capacitor CF and the feedback inductor LF. In addition, a size of the feedback inductor LF may increase based on a target frequency in order to compensate for a small size of the feedback capacitor CF. When an integrated circuit (IC) is manufactured, it may be difficult to include an inductor in the IC and the economic efficiency may be reduced due to the increased area of the inductor.